Bolt Torquing and Flange Material 2

The flange material shouldn't make a difference. However, the use of through-hardened washers (ASME PCC-1, Appendix M) should alleviate any concerns that you have. Without washers, I would be worried about galling under the nut.

Most piping flanges are assembled without washers...

MJCronin said:

Most piping flanges are assembled without washers...

Click to expand...

and the ones that leak due to insufficient bolt pre-load caused by galling between the nut and the flange will get repaired with through-hardened washers.


Of course, this assumes that you are using torquing as you assembly method. You are going to use some sort of controlled bolting, right?

TGS4, you are right assuming torquing as assembly method for small bolts. The 1" and larger bolts are using bolt tensioners for installation. Also, the bolt material matters, not the flange.
However, the use of washers is highly unusual in the hydrocarbon industry, where the leakage is a concern. There is no galling on the B7's, only in B8's on the 316 flanges. BTW, the B7 is rather unusual with duplex flanges and there is no galling on the Duplex flanges with any of SS bolts, perhaps it could be an issue with 316 flanges and 316 studs/nuts.

I have an archive of flange photos from leaking flanges that show damage to the underlying flange caused by the nut. Perhaps galling isn't the technically-correct term, but damage does occur, and the energy used to generate the damage is NOT converted to tensile bolt load.

gr2vessels said:

The 1" and larger bolts are using bolt tensioners for installation.

Click to expand...

Not sure where you got this from, but torquing is rather widely used. I just completed a report for a client where they were torquing a 1-7/8" bolt. I'd be happier if more bolted flange joints were assembled using any controlled-bolting technique. My experience is that most small (3/4" and less) aren't even torqued - just a hand-wrench or a hammer-wrench.

(Full disclosure: I spent my first summer job working at an oil production field. The first 3 weeks were spent closing up manways from vessels that had undergone their periodic inspection. I NEVER saw a torque wrench at all, but spent most of those 3 weeks striking a hammer wrench with a sledgehammer. If there was a leak during start-up, I was chided that it was because I wasn't swinging the sledgehammer hard enough...)

A good reference for studs and bolts :

There you go, please review the link below:


There is a lot on the internet regarding the hydraulic bolt tensioners. These are most common in the hydrocarbon industry. Ditch the spanner and the hammer. I hope that your first summer job was 20 years ago, not last year.

Cheers,
gr2vessels

Don't get me wrong - I think that hydraulic tensioning is a much preferred method. But, it's not the reality. Major ($5B+) new construction job, completed 6 years ago, called for torquing on bolts 1/2" and larger, and hydraulic tensioning for "high criticality" bolts only. Hydraulic tensioning is nice, but not when you have 6000+ flanges to assemble. Can't afford the time and cost...

Yes, that job was 20 years ago (will be this summer...).